Influence of bottom supporting columns and cooling rate on the surface shape characteristics of sapphire substrates

• Using graphite as the bottom supporting column in the sapphire crystal furnace reduced the vertical and horizontal temperature gradients inside the furnace. This was more conducive to preparing crystals with fewer bubbles and reduced defects such as solid inclusions. • Sapphire annealing was conducted using a one-step rapid annealing method. The average variations in warpage and bending rates in sapphire chips after annealing program D were the largest, reaching 1.5 μm and 0.5 μm, respectively. The total average variation was the largest, reaching 2.0 μm. • Sapphire chips were chemically corroded using molten KOH at a temperature of 360 °C for 16 min. The dislocation corrosion pits on the crystal surface were triangular, evenly distributed, and dispersed. The sapphire chips obtained by annealing using the D program and utilizing graphite as the bottom supporting column did not exhibit a U-shaped radial distribution with low center dislocation density and high edge dislocation density, nor a W-shaped radial distribution with high center and edge densities. The average dislocation density was low, at 108.89 pits/cm 2 . The manufacturing process of sapphire substrates involves several key steps, including epitaxy, annealing, cutting, and processing. Among these, epitaxy and annealing are particularly crucial. The temperature variances along both the longitudinal and transverse axes within the furnace during the crystallization process play a significant role in determining the crystallization rate and internal structure of sapphire crystals. Furthermore, annealing sapphire serves to alleviate internal stress, enhance crystal structure, optimize physical properties, improve optoelectronic characteristics, enhance surface quality, and increase overall yield. This step is paramount in enhancing the performance and application value of sapphire materials. In order to investigate and optimize the effects of different thermal conductivities of support columns at the base and various annealing procedures on the surface characteristics of sapphire substrates, thereby improving product quality, this study conducted research by utilizing support columns made of different materials and carefully controlling the cooling rate parameters for sapphire. The findings revealed that using graphite as the base support column for the crystal furnace can reduce both the longitudinal and transverse temperature gradients within the furnace, consequently promoting crystal growth and enhancing the quality of sapphire ingots. Additionally, sapphire chips annealed using the rapid one-step annealing program exhibited the highest average warpage and bending rate variation, reaching 2.0 μm, and the average dislocation density was half that of conventionally produced chips, at 108.89 pits/cm 2 .